Transistor ignition system

ABSTRACT

A RELATIVE TRANISTOR IGNITION SYSTEM THAT CAN BE INSTALLED IN EXISTING AUTOMOBILES WITHOUT REPLACING THE COIL INCLUDES A MULTIPOLE MAGNET ATTACHED TO THE DISTRIBUTOR SHAFT, A MAGNETIC FIELD SENSING DEVICE ADJACENT THE MAGNET, AND AN AMPLIFER-CONTROL THAT USES HIGH VOLTAGE, HIGH POWER TRANSISTORS.

Dec. 12, 1972 R. G. MoYER ErAL 3,705,-988

` TRANSISTOR IGNITION SYSTEM Filed April 18, 1971 SEA/SOR /NVE/VTORS RONALD G. MOYER THOMAS M. EMORYJR United States Patent Oihce U.'S. Cl. 307-10 R Claims ABSTRACT OF THE DISCLOSURE A reliable transistor ignition system that can be installed in existing automobiles without replacing the coil includes a multipole magnet attached to the distributor shaft, a magnetic field sensing device adjacent the magnet, and an amplifier-control that uses high voltage, high power transistors.

This inventon relates to a transistor ignition system. More particularly, this inventon relates to a transistor ignition system that is highly reliable and can be quickly and easily installed in existing automobiles with only simple modification of the distributor.

It has been known for a number of years that electronic switching of the ignition coil to generate voltages for the spark plugs would be an improvement over the existing mechanical switching techniques now being used. With the advent of the transistor, it was thought that at last a means for electronically controlling the switching of the ignition system was at hand. After an initial flurry, transistor ignition systems unfortunately proved to be defective. Their main drawback Was that they were unreliable. It would not operate at all at extreme temperature conditions. Moreover, their voltage capability Would fall off within the Operating ranges thereby resulting in poor sparking conditions.

Because of the initial poor quality of transistor ignition systems, a great deal of research, development and other inventive activity was undertaken. The result was the issuance of a large number of patents disclosing ignition systems which improved upon the initial ignition systems. These patents and other known systems disclose rather complex arrangements for avoiding the various problems encountered in transistor ignition systems.

Despite the great amount of activity in the field, the fact remains that as of today all major manufacturers of automotive equipment are still using mechanical switching techniques for their ignition systems. None has adopted a transistorized ignition. It would be impossible to analyze the reason in every instance. However, for the most part the reason why no system has been adopted is to be found in the fact that known operable systems appear to be so highly complex that they become commercially unfeasible. Typically, the transistor ignition system should be technically simple and highly reliable. Unfortunately, these two concepts are somewhat divergent.

The present inventon is directed toward an improved transistorized ignition system which reaches the goals of high reliability and technical simplicity. In accordance with the present inventon, the cam and points are replaced by a multipole magnet and a sensor which controls a transistor-control amplifier. The amplifier-control incorporates only two transistors which have been designed to vvithstand high power and high voltage. The output transistor controls the circuit between the automotive source of energy and ground. The system is unique in that there is no need to modify existing automotive ignition systems except to remove the points.

Patented Dec. 12, 1972 It therefore is an object of the present inventon to provide a new, reliable and technically simple transistor ignition system.

It is another object of the present inventon to provide a transistor ignition system that has an Operating life well in excess of the normal life of a vehicle.

It is another object of the present inventon to provide a transistor ignition system that uses a multipole magnet and magnetic sensor in place of the cam and points.

It is another object of the present inventon to provide a transistorized ignition system that uses either a reed switch or a magnistor to sense the field of the rotating multipole magnet.

It is another object of the present inventon to provide a transistorized ignition system that can be readily installed into existing automobiles with only minor modification, and no modification of the coil or ballast resistor.

It is another object of the present inventon to provide a transistorized ignition system having an amplifier-control that uses high voltage, high power silicon transistors.

It is yet another object of the present inventon to provide a transistor ignition system that can be used with standard ignition points. I

Other objects will appear hereinafter.

For the purpose of illustrating the inventon, there is shown in the drawings a form which is presently preferred; it being understood, however, that this inventon is not limited to the precise arrangements and instrumentalities shown.

FIG. 1 is a schematic block diagram of a transistorized ignition system in accordance with the present inventon.

FIG. 2 is a schematic diagram of the amplifier used in accordance with the present inventon.

Referring now to the drawing in detail, wherein like numerals indicate like elements, there is shown in FIG. 1 a schematic block diagram of a transistor ignition system constructed in accordance with the present inventon and designated generally as 10. As shown, the ignition system 10 includes a multipole permanent magnet 12 mounted for rotation on the distributor rotor. Positioned immediately adjacent to the magnet 12 is va magnetic sensor 14 which senses changes in the magnetic field as the magnet 12 rotates past it. The magnetic sensor 14 controls the transistor amplifier-control 16 by turning it on and off. As shown, the transistor amplifiercontrol 16 is connected in circuit with the primary of the ignition coil 18.

The primary of the ignition coil 18 is connected in series between the transistor amplifier-control 16 and the ballast resistor 20. The conventional ballast resistor 20 is in turn connected to a source of direct current voltage as is conventional in any automotive ignition system. The ignition c0il118 is a conventional, factory installed ignition coil such as may be found on almost any automotive vehicle having an intemal combustion engine. The secondary of the ignition coil '18 is connected through a distributor to the spark plugs or glow plugs for an intemal combustion engine.

'In operation, the magnetic sensor 14 responds to the changing magnetic field generated by the rotating multipole magnet 14 to control the transistor amplifier-control 16. Transistor amplifier-control 16 s controlled by rendering it conductive and non-conductive in phase with the poles of the magnet '12. When the transistor amplifiercontrol 16 is conductive, a pulse of current lflows through the primary of ignition coil 18 to thereby induce the necessary high voltage in the ignition coil secondary for the spark.

The multipole permanent magnet 12 is designed so as to fit onto the distributor shaft and to rotate with it. The permanent magnet 12 is designed to have suflicient north and south poles spaced uniformly around its periphery to operate the magnetic sensor 14. Although the perma-- nent magnet '12 is illustrated in FIG. 1 as having well defined pole pieces, it should be understood that other permanent magnets, some of which are perfectly cylindrical, could be substituted for the illustrated permanent magnet 12. When used to replace existing mechanical switching systems, the permanent magnet 12 can be designed to fit over the rotor.

The magnetic sensor 14 is positioned immediately adjacent to permanent magnet 12 so as to be afiected by its rotating magnetic field. In one preferred embodiment of the present invention, the magnetic sensor is designed so as to be placed in the same position as the breaker points of a conventional automotive system. For this p'urpose, the support structure for the magnetic sensor can be designed so that bolts or other fastening devices fit into the threaded holes used for the breaker contacts which are removed and discarded when installing an ignition system constructed in accordance with the present invention. I

'Ihe magnetic sensor l14 is preferably a magnetically Sensitive switch such as a reed switch. As an alternative, the magnetic sensor 1-4 may be a silicon magnistor such as is made by Hudson, Inc. Of course, other, equivalent, magnetically Sensitive switches can be used. As best illustrated in FIG. 2, the purpose of the magnetic sensor is to complete the circuit between the amplifier-control 16 and ground. If a reed switch is used, it can be positioned so as to close each time a pole piece of one polarity passes and open when the next succeeding pole piece of opposite polarity passes it. The number of poles for the permanent magnet 12 is chosen to accommodate 4, 6 and 8 cylinder engines mannfactured by major automotive companies. 'Of course, the configuration of the magnet can be modified for a larger or lesser number of cylinders, as desired.

Referrng now to FIG. 2, there is shown a transistor amplifier-control 16 constructed for use With the ignition system. As shown, the magnetic sensor 14 is connected through the resistor 22 to the base of the amplifier transistor 24. The emitter of Vtransistor 24 is connected to the positive side of the voltage supply and to the positive terminal of the primary of ignition coil 18. The collector of transistor 24 is connected through resistor 26 to the base of the control transistor 28. Resistor 30 is connected between the base andemitter of transistor 24 to provide appropriate bias voltage.

The collector of transistor 28 is connected to the opposite terminal of the primary of ignition coil 18. The emitter of transistor 28 is connected to the base through resistor 32 to provide appropriate voltage bias. A Zener diode 34 is connected, as shown, across the collector and emitter terminals of the transistor 28 in parallel with the capacitor 36. The emitter of transistor 28 is connected to Vground as shown.

In operation, the rotating multipole permanent magnet causes the magnetic sensor switch to complete a circuit between the resistor 22 and ground. This changes the bias on the base of amplifier transistor 24 and causes it to conduct. As a result, the |bias on the base of control transistor 28 is changed and it in turn conducts. When transistor 28 conducts, current flows through the primary of ignition coil 18 to ground.

As the multipole magnet 12 continues to rotate, the magnetic sensor 18 opens, thereby removing the bias on the base of amplifier transistor 24. Transistor 24 ceased to conduct and therefore so does control transistor 28. As a result, the magnetic field generated by the primary of the ignition coil 18 collapses and the spark is generated in a conventional manner.

In accordance with conventional magnetic theory, a

high reverse voltage occurs when transistor 28 becomesV 4.V a the reverse voltage from exceeding the breakdown voltage of the transistor.

Transistors 24 and 28 are the only transistors in the amplifier control :16. The function of amplifier transistor 24 is to provide sufiicient gain to operate control transistor 28. In effect, transistor 24 isolates transistor 28 from the magnetic sensor 14. Accordingly, the magnetic sensor 14 can be operated at low current levels to thereby increase its Operating life. In one embodiment'of the invention, the transistor 24 may be a Motorola 2M4898PNPV transistor rated at 3 amps and 25 watts.

It has been found that for good, reliable operation, the transistor 28 should be a high power, high 'voltage transistor. By way of example, transistor 28 could be a Delco DTS430NPN silicon transistor rated at 450 volts, Watts and 10 amperes. In combination with transistor 24 Operating at a gain of about 2.00; transistor 28 provides good control over the coil over more than the normal Operating temperatures under the hood of a standard American automobile such as a 1968 Cadillac. w

Since the amplifier 16 operates with a conventional factory ignition coil 18, it can be placed in any convenient position underneath the hood of the automobile. For example, it can be physically strapped to the coil itself.

Referring again to' FIG. 2, there is shown in dotted line a resistor 38 connected between one terminal of the ignition coil 18 and the magnetic sensor 14. Resistor 38 is shown in dotted line because it is intended to be added to the circuit only in the event that the magnetic sensor 14 and permanent magnet 12 are not incorporated; that is, the amplifier-control 16 is operated through the use of conventional breaker points.

From the foregoing, it should be apparent that the amplifier-control circuit 16 used with the ignition system 10 consists of a high voltage power transistor 28 driven by a one transistor amplifier `which in turn is controlled by a signal originating from the magnetic sensor 14. The signal is obtained through the detection of a rotating magnetic field and it is timed in the same way as the signal normally obtained from the use of breaker points. The advantage of such a circuit is that no adjustments for point gap or block alignment are required as there are no cams to wear and no points to be replaced. Of course, the entire circuit 16 is mounted in an appropriate container with means for adequate heat dissipation.

The present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof and, accordingly, reference should be made to the appended claims, rather than to the foregoing specification as indicating the scope of the invention.

We claim:

1. An ignition system for an internal combustion engine comprising a multipole permanent magnet adapted to be fixed to the shaft of a distributor, each adjacent pole of said multipole permanent magnet being of opposite polarity, magnetically responsve switch means responsve to the polarity of a magnetic field, said magnetically responsive switch means being mounted adjacent said multipole permanent magnet within a varying magnetic field generated by the rotation of said multipole permanent magnet, said magnetically responsve switch means being opened in response to a first predetermined magnetic field condition generated by said rotating multipole permanent magnet and being closed in response to a second predetermined magnetic field condition generated by said rotating multipole permanent magnet, a first transistor amplifier circuit, said first transistor amplifier circuit including a transistor having a base and a collector circuit, means for biasing said base circuit of said transistor, said biasing means including said magnetically responsve switch, said transistor being turned on and off in response to said closing and opening of said magnetically responsve switch, said collector circuit of said transistor developing an output signal, said output signal being supplied to a second transistor amplifier circuit, said second transistor amplifier circuit including a high power, high voltage transistor having a base, collector and emitter, said output of said collector circuit of said transistor of said first transistor amplifier crcuit being supplied to said =base of said transistor of said second transistor amplifier circuit, the emitter-collector circuit of said transistor in said second transistor amplifier circuit being connected in series with an ignition coil and a source of electrical potential energy, said transistor of said first transistor amplifier circuit and said transistor of said second transistor amplifier crcnit being the only transstors required, said second transistor amplifier allowing conduction through said ignition coil only When said first transistor amplifier conducts in response to operation of said magnetically responsive switch by the magnetic field generated by said rotating mnltpole permanent magnet. v

2. An ignition system in accordance with claim 1 wherein said magnetically responsive switch means is a reed switch.

3. An ignition system in accordance with claim 1 wherein said magnetically responsive switch means is a magnistor.

4. An ignition system in accordance with claim 1 wherein said transistor in said second transistor amplifier circuit is a silcon power transistor.

5. An ignition system in accordance with claim 1 including a breakdown device having a predetermined breakdown potential and a capacitor connected in parallel, said parallel connected breakdown device being connected across the emitter-collector circuit of said transistor in said second transistor amplifier circuit.

References Cited UNITED STATES PATENTS 3,072,824 1/1963 Short 123-148 E 3,29l,l09 12/1966 Neapolitakis 123-148 E 3,340,86l 9/1967 Schiff 123-148 E 3,374,778 3/1968 Dixon 123-148 E ROBERT K. SCHAFFER, Primary Examiner W. J. SMITH, Assistant Examiner U.S. Cl. X.R. 123-148 E 

